This study is concerned with predicting the clinical outlook for patients with congenital aortic stenosis, pulmonic stenosis, and ventricular septal defect whether treated medically or surgically. This prediction is individualized according to age, cardiac catheterization data, electrocardiographic and x-ray findings, in addition to clinical symptoms and signs. Information will be obtained to provide a basis for evaluating the advisability of surgery in cases where the comparative merits of medical and surgical treatment are currently in doubt. Finally, information will be obtained to provide means of assessing important hemodynamic quantities indirectly, i.e., without cardiac catheterization. This assessment would be based jointly on electrocardiographic and roentgenographic data in addition to symptoms and signs, general characteristics and past data on the patient.